The short version
What are the options for charging an Apple macbook air without using mains power or a fuel generator?
The longer version
I am travelling to a remote property and need to charge my Macbook air several times over a 2-3 week period. The place has a 12 volt set up to run various things. Engel fridge, lights, small fan etc. I will also have access to whatever charging options are available in a 2009 vehicle.